CHAPTER 8—INTERVAL ESTIMATION MULTIPLE CHOICE 1. The absolute value of the difference between the point estimate and the population parameter it estimates is a. the standard error b. the sampling error c. precision d. the error of confidence ANS: B PTS: 1 TOP: Interval Estimation 2. When s is used to estimate σ , the margin of error is computed by using a. normal distribution b. t distribution c. the mean of the sample d. the mean of the population ANS: B PTS: 1 TOP: Interval Estimation 3. From a population with a variance of 900, a sample of 225 items is selected. At 95% confidence, the margin of error is a. 15 b. 2 c. 3.92 d. 4 ANS: C PTS: 1 TOP: Interval Estimation 4. A population has a standard deviation of 50. A random sample of 100 items from this population is selected. The sample mean is determined to be 600. At 95% confidence, the margin of error is a. 5 b. 9.8 c. 650 d. 609.8 ANS: B PTS: 1 TOP: Interval Estimation 5. In order to determine an interval for the mean of a population with unknown standard deviation a sample of 61 items is selected. The mean of the sample is determined to be 23. The number of degrees of freedom for reading the t value is a. 22 b. 23 c. 60 d. 61 ANS: C PTS: 1 TOP: Interval Estimation 6. If we want to provide a 95% confidence interval for the mean of a population, the confidence coefficient is a. 0.485 b. 1.96 c. 0.95

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1.645 ANS: C PTS: 1 TOP: Interval Estimation 7. As the number of degrees of freedom for a t distribution increases, the difference between the t distribution and the standard normal distribution a. becomes larger b. becomes smaller c. stays the same d. None of these alternatives is correct. ANS: B PTS: 1 TOP: Interval Estimation 8. For the interval estimation of μ when σ is known and the sample is large, the proper distribution to use is a. the normal distribution b. the t distribution with n degrees of freedom c. the t distribution with n + 1 degrees of freedom d. the t distribution with n + 2 degrees of freedom ANS: A PTS: 1 TOP: Interval Estimation 9. An estimate of a population parameter that provides an interval of values believed to contain the value of the parameter is known as the a. confidence level b. interval estimate c. parameter value d. population estimate ANS: B PTS: 1 TOP: Interval Estimation 10. The value added and subtracted from a point estimate in order to develop an interval estimate of the population parameter is known as the a. confidence level b. margin of error c. parameter estimate d. interval estimate ANS: B PTS: 1 TOP: Interval Estimation 11. If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be a. 0.1 b. 0.95 c. 0.9 d. 0.05 ANS: C PTS: 1 TOP: Interval Estimation 12. Whenever the population standard deviation is unknown and the population has a normal or near-normal distribution, which distribution is used in developing an interval estimation? a.

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